Newly unsealed documents show that a Live Nation regional director boasted of gouging ticket buyers and "robbing them blind" with fees for ancillary services such as slight upgrades to parking. Live Nation has tried to exclude Slack messages from a trial that seeks a breakup of Live Nation and its Ticketmaster subsidiary, claiming the messages are irrelevant to the case, "highly prejudicial," and would "inflame the jury." The US government and state attorneys general opposed the motion to exclude evidence. US District Judge Arun Subramanian of the Southern District of New York hasn't ruled on the motion yet, but ordered the documents unsealed yesterday.…